The growth of wireless traffic has been significant in the last decade. Wireless devices, such as smartphones and tablet personal computers (PCs), have become ubiquitous, and due to their enhanced connectivity and the wide use of applications requiring data transmission, such devices and their applications use significantly more spectrum than feature phones or standard mobile devices (as much as 122 times for some tablet PCs, for example). And the market size for mobile broadband services continues to grow. Recent studies have predicted that the market for mobile broadband services may grow from 1 billion users in 2012 to around 8 billion users in 2015. In addition, global mobile data more than doubled for the fourth year in a row in 2011, and it will likely continue to do so in the predictable future. Accordingly, more spectrum is needed for mobile broadband use.
Traditionally, wireless devices have exclusively used dedicated bands, and if additional spectrum was needed for mobile broadband, it was created by repurposing spectrum (i.e., moving primary spectrum users to other bands). However, with time, the practice of repurposing has become more difficult and less feasible due to the nature of primary spectrum user services that would need to be moved to other bands. In particular, repurposing of existing services that are widely in use would be an extremely costly and lengthy undertaking, as confirmed by a recent report that concluded that potential repurposing of the 1755-1850 MHz band would take 10 years and cost some 18 billion dollars. As a result, regulators have begun to realize that methods other than repurposing may be needed to obtain the new spectrum that will solve the bandwidth crunch.